<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <style>
      /* .tixing {
        //网上答案
        margin: 100px auto;
        border-bottom: 100px solid red;
        border-left: 50px solid green;
        border-right: 50px solid yellow;
        height: 0;
        width: 100px;
      } */
      .tixing{
        width: 50px;
        height: 0;
        border: 50px solid transparent;
        border-bottom: 50px solid red;
      }
    </style>
  </head>
  <body>
    <p>和朝上三角形思路一样，三角形是最后border撑起来的宽高一样 隐藏其余边框，梯形只用宽度加宽 这样上部有宽而不是一个尖</p> 
    <div class="tixing"></div>
  </body>
</html>
